请求将“Point*”转换为非标量类型的“Point”

Question

我读过几篇类似的文章，我要么不明白它们能提供什么，要么它们似乎不适用。我是新来的，尽我最大努力遵守规则。

我们在课程的最后两周学习c++，40小时后进入期末考试:)，所以我是个初学者。我对C很熟悉。

以下是任务中与此相关的部分：

Part 1 [20 points]
Reading material:
Copy constructor: https://www.geeksforgeeks.org/copy-constructor-in-cpp/
References (the & symbol): https://www.geeksforgeeks.org/references-in-c/
------------------------------------------------------------------------------------------------------
Write a class Point representing a point in 2d.
The class will have the following public methods:
// constructor - sets the coordinates to be x,y
Point( int x, int y)
// copy constructor - creates a new point with the same
coordinates
Point(Point &copy)
// getters
int getX()
int getY()
// setters
void setX()
void setY()
// prints to screen the coordinates in the format (x,y)
void print()

我的执行情况：

Point.hpp

#include <iostream>

using namespace std;

class Point { 
   private: 
   int x, y; 

public: 
    // Parameterized Constructor 
    Point(int x1, int y1); 

    ~Point();

    Point (const Point &p2);

    int getX();

    int getY(); 


    void setX(int x2);


    void setY(int y2);

    void print();
};

Point.cpp

#include "Point.hpp"

Point::Point(int x1, int y1)
    { 
        x = x1; 
        y = y1; 
    } 
Point::Point (const Point &p2)
    {
        x = p2.x;
        y = p2.y;
    }

int Point::getX()
    { 
        return x; 
    } 

int Point::getY()
    { 
        return y; 
    } 

void Point::setX(int x2)
    {
      x = x2;
    }

void Point::setY(int y2)
    {
      y = y2;
    }

void Point::print()
    {
        cout << "(" << x << "," << y << ")";
    }

--问题的一部分--我被困在上了

Part 2 [20 points]
Reading material:
Abstract classes and pure virtual methods:
https://www.geeksforgeeks.org/pure-virtual-functions-and-abstract-classes/
---------------------------------------------------------------------------------------------------
Write an abstract class GeometricShape representing an abstract geometric
shape. The class will have the following public methods:
// Constructor: gets a coordinate. The purpose of the
coordinate depends on the specific shape
GeometricShape(Point coord)
// returns the area of the shape
// returns 0 as default. To be implemented in each
concrete shape
virtual float getArea() { return 0 ; }
// returns the perimeter of the shape
// returns 0 as default. To be implemented in each
concrete shape
virtual float getPerimeter() { return 0 ; }
// virtual method. To be implemented in each concrete
method
virtual void print() = 0 ;

我的执行情况：

GeometricShape.hpp

#include <iostream>
#include "Point.hpp"

using namespace std;

class GeometricShape { 

private:
    Point point;

public: 
    // Parameterized Constructor 
    GeometricShape(Point coord); 

    virtual float getArea();

    virtual float getPerimeter(); 

    virtual void print() = 0;
};

GeometricShape.cpp (，这是不会编译的东西)

#include <iostream>
#include "GeometricShape.hpp"


GeometricShape::GeometricShape(Point coord)

{

Point p = new Point(coord.getX(),coord.getY());


}

int main()
{
  return 0;
}

在Linux Ubunto 18.04.3 (远程访问的大学实验室，在实验室中编译所需的任务)上编译时的错误消息

错误消息：

gsg27@csil-cpu2:~/sfuhome/cmpt-125/5$ g++ GeometricShape.cpp
GeometricShape.cpp: In constructor ‘GeometricShape::GeometricShape(Point)’:
GeometricShape.cpp:9:11: error: conversion from ‘Point*’ to non-scalar type ‘Point’ requested
 Point p = new Point(coord.getX(),coord.getY());
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Answer 1

你眼前的问题是

Point p = new Point(coord.getX(),coord.getY());

没有道理。new表达式返回指向动态分配对象的指针。所以，你写的代码应该是

Point *p = new Point(coord.getX(),coord.getY());

但是，您不需要指针，也不需要动态分配的对象:您只是尝试初始化一个数据成员。所以你的构造函数应该是

GeometricShape::GeometricShape(Point coord) : point(coord) {}

因为您已经拥有数据成员GeometricShape::point，并且Point类有一个副本构造函数。这样写起来会更平常

GeometricShape::GeometricShape(Point const &coord) : point(coord) {}

因为你不需要复制两份原件，但这里没什么大不了的。

Answer 2

在接受了上述所有帮助并咨询了我的教授之后：

它应该按以下方式实现，并且工作正常

#include <iostream>
#include "Point.hpp"

using namespace std;

class GeometricShape { 

private:
    Point point;
    float area;
    float perimeter;

public: 
    // Parameterized Constructor 
    GeometricShape(Point coord) :  point(coord.getX(), coord.getY())  // initialize the data field
    {
      area = 0;
      perimeter = 0;
    }

    virtual float getArea();

    virtual float getPerimeter(); 

    virtual void print() = 0;
}; 

注意，因为它是一个抽象类，所以作为初学者，我觉得让所有的一个文件都不是hpp和cpp文件不那么让人费解。